package LuoGu.入门.对角线;

import java.math.BigInteger;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        BigInteger n = s.nextBigInteger();
        BigInteger ans = (n.multiply(n.subtract(new BigInteger("1"))).
                divide(new BigInteger("2")).multiply(n.subtract(new BigInteger("2"))).
                divide(new BigInteger("3")).multiply(n.subtract(new BigInteger("3"))).
                divide(new BigInteger("4")));
        System.out.println(ans);
    }
}
